The Research Of Measure To Prevent Long-span PC Girder Bridge From Crack And Defection

Currently,with the advantages of high structure stiffness,concise and beautifulstructure,good integrity and continuity,comfortable driving,fewer expansionjoints,and favorable maintenance etc,large span pretressed concrete bridge is widelyused in our country and predominantly in the bridges with span ranging from40m to200m.At the same time,all kinds of problem and disease have been appeared duringtheir operation.Among all problems and diseases,the down deflection and crack ofbeam are the most common phenomena,which have not been solved satisfactorilyuntil recently.Therefore,the research about diseases and the health monitoring of largespan pretressed concrete bridge is immensely important.Based on beijiang bridge.this paper in detail analyzes the causes of diseases andthe influence of diseases on the bridge performance according to the common diseasesexisting in large span bridges,and studies the design measures and constructionmethods of reducing mid-span deflection and beam cracks,the affect of them on theworking performance and the effect of them on reducing deflection and cracks.Themain study works are as follows:1. This paper in detail studied and summarized the diseases and causes of largespan pretressed concrete bridges based on the related investigation materials of theproject and referring relevant literatures,and investigated the present situation of thebridge.Some methods and measures to reduce the bridge diseases were proposedwhich are based on bridge constitution,design detail,construction technology.2. According to the design drawings,a3D model of beijiang bridge is build basedon the finite element software MIDAS and ANSYS.The structure performance andstress state are analyzed,and the stresses and deformations of the weak positions areinspected,then beijiang bridge’s numerical model will be modified by followingcritical parameters to imitate degeneration of the structure performance:longitudinaland vertical prestress loss,structural dead weight and the thickness of the bridge deckpavement,loading age,mid-span deflection.3. By implementing precaution and dominating common diseases, the followingmethods of reducing mid-span deflection and beam cracks are studied and contrasted:temporary presstressed reinforcing steel,push-put before closure,temporary towers forclosure,add steel skeletons on box girder soleplate,turn long presstressed reinforcingsteel to short presstressed reinforcing steel,oblique vertical presstressed reinforcing steel,compare the influence of these measures on reduce mid-span deflection andbeam cracks,finally some suggestions are proposed.